The waste gas in metal recycling usually contains particles (abraded metal, mineral dust), inorganic, acid substances (HF, HCI, SOx) and dioxins (PCDD/F) as well as a whole range of organic substances (unburned hydrocarbons) and carbon monoxide. Particularly, in the group of unburned hydrocarbons some substances such as phenols and formaldehydes with a very small odor threshold are tipically to be found. Even concentrations of few mg/Nm³ can cause an odor nuisance. Only with a regenerative thermal oxidation system (RTO) such odors can be eliminated economically.

Particles and inorganic substances are eliminated through the process of dry sorption by injecting an alkaline reagent in the waste gas duct. The reaction products and the overdosed reagents are eliminated in a downstream bag filter. By injecting heath furnace coke, active coke and zeolite in addition to the alkaline reagent, dioxins are absorbed.

In order to make the system even more economical, it incorporates a heat recovery downstream the RTO which produces 4 MW of hot water for the municipality.

Conclusion: Thanks to this outstanding and highly economical air purification system, the incoming material does not have an influence on odor emissions. The operator is now able to use increasingly low-grade scrap.

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